System and method to access lung tissue

ABSTRACT

A system and method for navigating to a target site in a patient is provided. The system includes an extended working channel and a tool usable with an electromagnetic navigation system. In particular, the extended working channel and the tool contain an electromagnetic sensor configured to provide location information within a patient of the extended working channel and the tool to the electromagnetic navigation system. The distance from the tool and the target site can then be determined and displayed to a clinician on a display device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/683,576, filed on Nov. 14, 2019, which is acontinuation application of U.S. patent application Ser. No. 15/155,830,filed on May 16, 2016, now U.S. Pat. No. 10,478,254, the entire contentsof each of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates generally to systems and methods fornavigating a tool, such as a catheter, probe, or medical device, througha luminal network of a patient's body to a target site and tracking thelocation of the tool relative to the target site.

A common device for inspecting and navigating the airway of a patient isa bronchoscope. Typically, the bronchoscope is inserted into a patient'sairways through the patient's nose or mouth and can extend into thelungs of the patient. In navigating to a region of interest,bronchoscopes, however, are limited in how far they may be advancedthrough the airways due to their size. In instances in which thebronchoscope is too large to be located at a region of interest deep inthe lungs, a clinician may advance smaller diameter catheters and/ortools through the bronchoscope to reach the location. To aid in thenavigation of the catheter and/or tool through the bronchoscope, theclinician may utilize real-time imaging modalities such as computerizedtomographic (CT) images. These images enable the development ofthree-dimensional models of the airways or other luminal networks,typically from a series of computed tomography (CT) images. While thesystem described above is quite capable, improvements may be made.

SUMMARY

Provided in accordance with the present disclosure is a method ofnavigating a tool to a target site. The method includes firstidentifying a location of a target site within a patient's body. Thelocation of a tool having a first sensor disposed on the tool is thentracked and a distance between the location of the target site and thetracked location of the tool first sensor is determined. The tracking ofthe location of the first sensor may include receiving orientation datacorresponding to the first sensor. In an embodiment, the tool is aneedle, a guide wire, a biopsy tool, a dilator, or an ablation device.The determined distance between the location of the target site and thetool is then displayed. The identification of a location of a targetsite within a patient's body may include obtaining a plurality of imagesof the patient's body and then identifying the location of the targetsite from the plurality of images, the plurality of images may be storedimages. The plurality of images may also include computer tomography(CT) images, ultrasound images, magnetic resonance images (MRI),fluoroscopic images, or endoscopic images. Additionally, the location ofthe target site may be identified by displaying images of the patient'sbody and receiving an input on one or more of the images indicating thelocation of the target site. In one embodiment, the target site mayinclude a biomarker or other localization materials, which can be usedto identify the location of the target site and sensed by the firstsensor.

In one embodiment, the method further includes detecting a change inlocation of the first sensor on the tool and determining a distancebetween the location of the target site and the change in location ofthe first sensor. The displayed distance between the location of thetarget site and the first sensor is then updated. The method may furtherinclude the tracking of a location of a second sensor on a catheterconfigured to receive the tool and determining a distance between thelocation of the first sensor and the second sensor. The distance betweenthe location of the first sensor and the second sensor is thendisplayed. The catheter may be an extended working channel (EWC), aneedle, a guide wire, a biopsy tool, a dilator, or an ablation device.

Also provided in accordance with the present disclosure is a navigationsystem including a tool configured to be advanced through a patient'sluminal network, the tool having a first sensor, a display configured todisplay an image of a portion of the patient's luminal network, acontroller coupled to the display, and a memory. The memory storesinstructions that when executed by the controller cause the controllerto identify a location of a target site within a patient's body, track alocation of the tool having the first sensor, determine a distancebetween the location of the target site and the tool, and display, onthe display, the distance between the location of the target site andthe tool. The tool may be an extended working channel (EWC), a needle, aguide wire, a biopsy tool, a dilator, or an ablation device. Thenavigation system may further comprise a catheter configured to receivethe tool, the catheter having a second sensor. In an embodiment, thefirst sensor and/or the second sensor may be an electromagnetic sensor.In an embodiment, the memory further causes the controller to track alocation of the catheter having the second sensor, determine a distancebetween the location of the tool and the catheter, and display, on thedisplay, the distance between the location of the tool and the catheter.

In an embodiment, the tool is lockable relative to the catheter. Thetool can be locked to the catheter with a clip, luer lock, or a thread.In another embodiment, the tool includes a hub wherein the first sensoris disposed circumferentially around the hub.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described herein withreference to the drawings wherein:

FIG. 1 is a schematic illustration of an electromagnetic navigation(EMN) system and two catheter guide assemblies configured to be usedwith the EMN system, in accordance with an embodiment of the presentdisclosure;

FIG. 2 is a perspective view of a catheter guide assembly of the EMNsystem of FIG. 1 , in accordance with the present disclosure;

FIG. 2A is an enlarged view of an embodiment of a distal portion of thecatheter guide assembly of FIG. 2 indicated by area “A”;

FIG. 2B is an enlarged view of an alternative embodiment of the distalportion of the catheter guide assembly of FIG. 2 indicated by area “A”;

FIG. 2C is an enlarged view of another alternative embodiment of thedistal portion of the catheter guide assembly of FIG. 2 indicated byarea “A”;

FIG. 3 is a schematic of the components of a workstation that may beimplemented in the EMN system of FIG. 1 , in accordance with anembodiment of the present disclosure;

FIG. 4 is a flow diagram of a method for navigating a catheter and atool to a target site, in accordance with an embodiment of the presentdisclosure;

FIG. 5 is a perspective partial-view of a distal portion of anembodiment of a catheter and a tool in a surgical site, in accordancewith the present disclosure;

FIG. 6 is a flow diagram of a method for navigating a catheter and atool to a target site, in accordance with another embodiment of thepresent disclosure; and

FIG. 7 is a perspective partial-view of a distal portion of anembodiment of a catheter and a tool in a surgical site, in accordancewith another embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to a navigation system and a methodfor determining and displaying the distance between a tool and a targetsite. Generally, a sensor is included on the tool to thereby permit thesensing and tracking of the tool's location. Using the location of thetool, the system calculates a distance between the tool and the targetsite, and displays the distance to a user. The system may detectmovement of the sensor, causing the distance between the tracked tooland the target site to be recalculated and the display to be updatedwith the recalculated distance.

Detailed embodiments of the present disclosure are disclosed herein;however, the disclosed embodiments are merely examples of thedisclosure, which may be embodied in various forms. Therefore, specificstructural and functional details disclosed herein are not to beinterpreted as limiting, but merely as a basis for the claims and as arepresentative basis for teaching one skilled in the art to variouslyemploy the present disclosure in virtually any appropriately detailedstructure.

FIG. 1 shows an electromagnetic navigation (EMN) system 130 configuredfor use with a catheter guide assembly 110, 112, in accordance with anillustrative embodiment of the present disclosure. The EMN system 130 isconfigured to utilize computerized tomography (CT) imaging, magneticresonance imaging (MRI), ultrasonic imaging, endoscopic imaging,fluoroscopic imaging, or another modality to create a roadmap of apatient's lungs. One such EMN system 130 is the ELECTROMAGNETICNAVIGATION BRONCHOSCOPY® system currently sold by Medtronic Inc. The EMNsystem 130 generally includes a bronchoscope 126 configured to receiveone or more types of catheter guide assemblies 110, 112, monitoringequipment 138, an electromagnetic field generator 142, a tracking module132, and a workstation 136. FIG. 1 also depicts a patient “P” lying onan operating table 140 including an electromagnetic field generator 142.The positions of a number of reference sensors 144 placed on the patient“P” in the magnetic field generated by the electromagnetic fieldgenerator 142 can be determined by the tracking module 132. The EMNsystem 130 uses the reference sensors 144 to calculate a patientcoordinate frame of reference.

Each of the catheter guide assemblies 110, 112 includes a control handle124 and an extended working channel (EWC) 116 that is configured toreceive a tool 100. The EWC 116 includes an electromagnetic (EM) sensor120 located on a distal end 118 of the EWC 116. The tool 100 may be anyone of a variety of medical devices including, but not limited to, aneedle, a guide wire, a biopsy tool, a dilator, or an ablation device.In an embodiment, the tool 100 also includes an EM sensor 102. The EMsensors 102, 120 work in conjunction with the tracking module 132 toenable tracking and navigation of the EM sensors 102, 120 within themagnetic field generated by the electromagnetic field generator 142. Inparticular, the tracking module 132 enables navigation and tracking ofthe EM sensors 102, 120, including receiving orientation datacorresponding to the EM sensors 102, 120, within a luminal network of apatient “P” to arrive at a target site. EM sensors 102, 120 may be anynumber of types of location sensors, including ring sensors, opticalsensors, radiofrequency sensors, ferromagnetic sensors, hollow sensors,and the like. In an embodiment where EM sensor 120 is a hollow sensor,the hollow sensor can be configured to measure a distance that the tool100 advances past the distal end 118 of the EWC 116.

With additional reference to FIG. 2 , a catheter guide assembly 110 isshown, in accordance with an embodiment of the present disclosure. Inaddition to including the EWC 116 and tool 100, the catheter guideassembly 110 includes a control handle 124, which enables advancementand steering of the distal end of the catheter guide assembly 110. Onceinserted in the EWC 116, the tool 100 can be locked to the EWC 116 witha locking mechanism 122. The locking of tool 100 to the EWC 116 allowsthe tool 100 and the EWC 116 to travel together through a luminalnetwork of the patient “P.” The locking mechanism 122 may be a simpleclip or luer lock, or the tool 100 may have a threaded configurationthat allows it to threadably engage with and lock to the EWC 116.Examples of catheter guide assemblies usable with the instant disclosureare currently marketed and sold by Medtronic Inc. under the nameSUPERDIMENSION® Procedure Kits and EDGE™ Procedure Kits. For a moredetailed description of the catheter guide assemblies, reference is madeto commonly-owned U.S. Patent Application Publication Number2014/0046315 filed on Mar. 15, 2013, by Ladtkow et al. and U.S. Pat. No.7,233,820, the entire contents of which are incorporated in thisdisclosure by reference.

FIG. 2A is an enlarged view of a distal end of the catheter assembly 110indicated by an encircled area “A” in FIG. 2 . Here, the EWC 116including an EM sensor 120 is shown receiving a tool 100, which on itsdistal end includes an EM sensor 102. FIG. 2B depicts a differentembodiment of the distal end of the catheter assembly 110 except that inthis embodiment, the EWC 116 does not include an EM sensor. FIG. 2Cdepicts yet another embodiment of the catheter assembly 110 in which theEM sensor 102 is disposed at a location that is closer to a proximal endof the tool 100. No matter the particular configuration, the EM sensors102, 120 on the distal portion of the EWC 116 and/or the tool 100 aresensed by the electromagnetic field produced by the electromagneticgenerator, and are used to identify the location of the EWC 116 and/orthe tool 100 in the electromagnetic field. The EM sensors 102, 120 areused to navigate the EWC 116 and/or tool 100 through a luminal networkof the patient “P.” In this particular embodiment, the luminal networkis the patient's lung.

As noted briefly above, the tracking module 132 receives data receivedfrom the EM sensors 102, 120 and provides the data to the workstation136 for use in planning and navigation. Turning now to FIG. 3 , in orderto operate as described, workstation 136 may include memory 204,processor 202, display 214, network interface 212, input device 216,and/or output module 218. Memory 204 includes any non-transitorycomputer-readable storage media for storing data and/or software that isexecutable by processor 202 and which controls the operation ofworkstation 136. In an embodiment, memory 204 may include one or moresolid-state storage devices such as flash memory chips. Alternatively orin addition to the one or more solid-state storage devices, memory 204may include one or more mass storage devices connected to the processor202 through a mass storage controller (not shown) and a communicationsbus (not shown).

Memory 204 may store application 208 and/or image data 206. Application208 may, when executed by processor 202 cause a display associated withworkstation 136 to present user interface 210. Network interface 212 maybe configured to connect to a network such as a local area network (LAN)consisting of a wired network and/or a wireless network, a wide areanetwork (WAN), a wireless mobile network, a Bluetooth network, and/orthe internet. Input device 216 may be any device by means of which auser may interact with workstation 136, such as, for example, a mouse,keyboard, foot pedal, touch screen, and/or voice interface. Outputmodule 218 may include any connectivity port or bus, such as, forexample, parallel ports, serial ports, universal serial busses (USB), orany other similar connectivity port known to those skilled in the art.

Prior to the start of navigation, a clinician loads a navigation planinto application 208 from memory 204, a USB device, or from networkinterface 212. During a procedure planning phase, the workstation 136utilizes computed tomographic (CT) image data or other image dataobtained using a different modality, for generating and viewing athree-dimensional model of patient “P's” airways. This process enablesthe identification of target site “T” (shown in FIG. 5A) to be navigatedto in the image data and to coordinate that target with athree-dimensional model (automatically, semi-automatically, ormanually). The planning software allows for the selection of a pathwaythrough the patient “P's” airways to target site “T.” More specifically,the CT scans are processed and assembled into a three-dimensional CTvolume, which is then utilized to generate a three-dimensional model ofthe patient “P's” airways. The three-dimensional model of the patient“P's” airways may be displayed on a display associated with workstation136, or in any other suitable fashion. Using the workstation 136,various views of the three-dimensional model of the patient “P's”airways or two-dimensional images generated from the three-dimensionalmodel of the patient “P's” airways may be presented. Thethree-dimensional model of the patient “P's” airways or thetwo-dimensional images of the patient “P's” airways may be manipulatedto facilitate identification of target site “T.” Additionally, thetarget site may be identified by detecting a biomarker placed at thetarget site. The biomarker may also be the tool 100. Thereafter, asuitable pathway through patient “P's” airways to access target site “T”can be selected. After a suitable pathway is selected, the pathway issaved and exported to a navigation component of the software for useduring the navigation phase(s).

Once the pathway to the target is selected, the EMN system 130 utilizesthe EM sensors 102, 120 on the EWC 116 in conjunction with the trackingmodule 132 to enable tracking and navigation of the EM sensor 102, 120towards the target site “T.” As shown in FIG. 1 , the clinician insertsa catheter guide assembly 110, 112 including an EM sensor 102, 120 intoa bronchoscope 126 for navigation through a patient “P's” airways.Utilizing the tracking module 132, the location of the EM sensor 102,120 within the three-dimensional model of the patient “P's” airways canbe viewed on the workstation. Using the location of the EM sensor 102,120 and the three-dimensional model of the patient “P's” airways, theclinician can maneuver and guide the EWC 116 and the tool 100 to thetarget site “T.”

With additional reference now to FIG. 4 , a flowchart is provided of acomputer-implemented method 400 of navigating to a target site “T” andtracking the distance of a tool 100 to a target site “T.” The method 400may be implemented, at least in part, by the processor 202 executinginstructions stored in the memory 204 (FIG. 3 ). Additionally, theparticular sequence of steps shown in the method 400 may be executed insequences other than the sequence shown in FIG. 4 without departing fromthe scope of the present disclosure. Further, some steps shown in method400 of FIG. 4 may be concurrently executed with respect to one anotherinstead of sequentially executed with respect to one another.

In an embodiment, the method 400 starts with a plurality of images of apatient being received at S401. For example, the plurality of images maybe images of a patient's body that are captured using one or more of avariety of imaging modalities including, but not limited to,computerized tomography (CT) imaging, magnetic resonance imaging (MRI),ultrasound imaging, endoscopic imaging, or fluoroscopic imaging.

At S402, a target site “T” is identified within the patient's body usingthe images. As described in further detail above, in an embodiment, oneor more of the plurality of images obtained in S401 are used by the EMNsystem 130 to identify and plan a pathway to reach the target site “T.”

As shown in FIG. 4 , an electromagnetic field generator generates anelectromagnetic field around the patient in S403. In this regard, anumber of reference sensors 144 placed on the patient “P.” Theelectromagnetic field generator 142 and the reference sensors 144 areinterconnected with tracking module 142, which derives the location ofeach reference sensor 144 in six degrees of freedom. The six degrees offreedom coordinates of reference sensors 144 are sent to workstation 136where reference sensors 144 are used to calculate a patient coordinateframe of reference.

Next, the location of a catheter and/or a tool is tracked at step S404.For example, a catheter, such as EWC 116, is inserted into the patient,where the catheter includes a first EM sensor 120. In an embodiment, theEWC 116 is inserted into a bronchoscope 126. A tool 100 having a secondEM sensor 102 is then advanced through the EWC 116. Using the pathwayselected during the planning phase, described in detail above, the EWC116 and tool 102 are navigated towards a target site “T,” as shown inFIG. 5 . Utilizing the electromagnetic field generator 142 and thereference sensors 144 interconnected with tracking module 142, the EMNsystem 130 tracks the location of both the EM sensor 120 on the EWC 116or catheter and the EM sensor 102 on the tool within the patientcoordinate frame of reference in S404.

A detection is made as to a change in the location of the tool at stepS405. For example, after the EWC 116 and the tool 100 are navigatedtowards the target site “T,” the workstation of EMN system 130calculates the distance “D1” (shown in FIG. 5 ) between the distal endsof the EWC 116 and the tool 100 using the EM sensors 102, 120. In anembodiment, the distance “D1” is zero when the distal end of tool 100 isaligned with the distal end of the EWC 116 so that as the tool 100 isadvanced past the distal end of the EWC 116, the distance “D1” increasesand the change in location of the tool 100 is detected.

A distance is then determined between the tool and a target site, atstep S406. For example, workstation 136 calculates the distance betweenthe tool 100 and the target site “T”. In an embodiment, since thelocation of the target site “T” is known based on the acquired CT imagesand generated planned pathway, the distance “D2” from the EWC 116 andthe target site can also be determined. As the tool 100 is advanced pastthe EWC 116, the distance from the tool 100 to the target site “T” canalso be determined.

The determined distance between the EWC 116 and the tool is displayed atstep 407. According to an embodiment, the calculated distance “D2” fromthe EWC 116 and the target site can then be displayed to a user byworkstation 136 in real time.

In another embodiment, in addition to the performance of step S406, adistance is calculated between the EWC 116 and the tool 100, at stepS406 a. As noted above, as a result of the detection of the change oflocation of the tool 100 in step S405, the distance “D1” may becalculated to indicate the distance the tool 100 is advanced past theEWC 116. Likewise, the calculated distance may be displayed at stepS407. For example, the distance “D1” from the EWC 116 and the tool 100can be displayed to the user. In another embodiment, as shown in FIG.2C, the EM sensor 102 may be disposed at a location that is closer to aproximal end of the tool 100. In such an embodiment, the EM sensor 102may not extend outside of the EWC 116. As the tool 100 advances forward,the EM sensor 102 inside the EWC 116 progressively moves toward the EMsensor 120 of the EWC 116, and the distance between the EM sensor 102inside of the EWC 116 and the EM sensor 120 of the EWC 116 can then beused to determine the distance “D1” between the distal end of the tool100 and the EM sensor 120.

In S408, a determination is made as to whether the tool 100 has advancedto the target site “T.” For example, a determination is made as towhether the distance between the tool 100 and the target site “T” iszero. If the tool 100 has not yet reached the target site “T,” the tool100 is advanced through the EWC 116 or catheter and the method 400reiterates at S405. As the display is updated at step 407, the displayeffectively provides a “counting-down” of the distance the tool 100needs to be advanced before it reaches the target “T.” For example, theworkstation 136 updates the display to display the updated distance “D2”between the tool 100 and the target site “T.” Likewise, the updateddistance “D1” between the EWC 116 and tool 100 can be displayed.Returning to step S408, if a determination has been made that the tool100 has reached the target site “T the process is complete. The tool 100may then be used to treat the target site “T” and/or it may be removedto allow a different tool to be inserted through the EWC 116 orcatheter.

With reference now to FIG. 6 , a flowchart is provided of acomputer-implemented method 600 of navigating to a target site “T” andtracking the distance of a tool 100 to a target site “T,” according toanother embodiment. The method 600 may be implemented, at least in part,by the processor 202 executing instructions stored in the memory 204(FIG. 3 ). Additionally, the particular sequence of steps shown in themethod 600 may be executed in sequences other than the sequence shown inFIG. 6 without departing from the scope of the present disclosure.Further, some steps shown in method 600 of FIG. 6 may be concurrentlyexecuted with respect to one another instead of sequentially executedwith respect to one another. The method 600 of FIG. 6 is described withreference to FIG. 7 .

Steps S601 to S604 are performed in a manner substantially similar tosteps S401 to S404 of FIG. 4 , respectively. At step S605, a detectionis made as to a change in the location of the tool. For example, whenthe distal end of tool 100 is aligned with the distal end of the EWC116, the distance is zero. However, as the tool 100 is advanced past thedistal end of the EWC 116 (or retracted), the distance between the twoincreases (or decreases) and the change in location of the tool 100 isdetected. In an embodiment in which the distal end of the tool 100 isadvanced past the distal end of the EWC 116, as shown in FIG. 7 , thedistal end of the tool 100 may be placed at a location “P1”.

A distance is then determined between the tool and a target site, atstep S606. For example, workstation 136 calculates the distance betweenthe tool 100 and the target site “T” using the sensor 102 on the distalend of the tool 100. In an embodiment, since the location of the targetsite “T” is known based on the acquired CT images and generated plannedpathway, the distance “D2” from the EWC 116 (for example, via the sensor120) and the target site “T” can also be determined. In particular, asthe tool 100 is advanced past the EWC 116, the distance from the tool100 to the target site “T” can also be determined (for example, thedistance “D4” in FIG. 7 ).

The determined distance between the EWC 116 and the tool is displayed atstep S607. According to an embodiment, the calculated distance “D2” fromthe EWC 116 and the target site “T” can then be displayed to a user byworkstation 136 in real time. Likewise, the distance “D4” between thetool 100 and the target site “T” is displayed to a user by workstation136 in real time, effectively “counting down” the distance remaining tothe target site “T.”

In another embodiment, in addition to the performance of step S606, adistance is calculated between the EWC 116 and the tool 100, at stepS606 a. As a result of the detection of the change of location of thetool 100 in step S605, the distance “D1” may be calculated to indicatethe distance the tool 100 has been advanced past the EWC 116. Likewise,the calculated distance may be displayed at step S607. For example, thedistance “D1” from the EWC 116 and the tool 100 can be displayed to theuser.

In step S608, workstation 136 stores a tracked location of the EWC 116,or catheter, and a tracked location of the tool 100 in memory 204. Forexample, referring to FIG. 7 , the location “P1” at a distal end of thetool 100 when the distance is “D1” may be stored. As the tool 100 isadvanced, a change in the location of the tool 100 is detected in stepS609, for example, to location “P2”. The change in distance “D3” betweenthe new location “P2” of the tool 100 and the stored location “P1” ofthe tool 100 is then determined in S610. Hence, as the tool 100 isadvanced past the distal end of EWC 116, the distance from the tool 100to the target site “T” also changes. In particular, the change inlocation of the tool 100 is determined to be “D3.” As the distance “D3”increases, the distance “D4” from the distal end of tool 100 to thetarget site “T” decreases in an equal amount.

The new distance “D5” between the new location “P2” of tool 100 and thetarget site “T” is then determined in step S611 a. Additionally, thedistance between the new location of tool 100 and the EWC 116 is alsodetermined in step S611 b. The can be determined adding the distance“D3” with distance “D1” to yield the distance “D6”. As such, as thedistance “D3” increases, the distance from the EWC 116 to the distal endof the tool 100 “D6” increases in an equal amount.

In step S612, the distance between the EWC 116 and the tool 100 “D6”and/or the distance “D5” between the tool 100 and the target site “T”are displayed on workstation 136. Additionally or alternatively, thechange in distance “D3” between the new location of tool 100 and thestored location of tool 100 can also be displayed. The displayeddistances can be continually updated to present a live “count-down” ofthe distance remaining from the tool 100 to the target site “T.”

In step S613, a determination is made as to whether the tool 100 hasadvanced to the target site “T.” For example, a determination is made asto whether the distance between the tool 100 and the target site “T” iszero. If the tool 100 has not yet reached the target site “T,” the tool100 is advanced through the EWC 116 or catheter and the method 400reiterates at S609.

Returning to step S613, if a determination has been made that the tool100 has reached the target site “T the process is complete. The tool 100may then be used to treat the target site “T” and/or it may be removedto allow a different tool to be inserted through the EWC 116 orcatheter.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting but merely asexemplifications of particular embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

What is claimed is:
 1. A navigation system, comprising: a catheterconfigured to be advanced through a patient's luminal network, thecatheter having a first sensor and defining a lumen; a tool configuredto be advanced through the lumen of the catheter, the tool having asecond sensor; a controller; and a memory storing instructions, whichwhen executed by the controller, cause the controller to: track alocation of the first sensor; track a location of the second sensor whenthe second sensor is in a first position within a patient coordinateframe of reference and when the second sensor is in a second positionwithin the patient coordinate frame of reference; determine a distancebetween a target and the location of the first sensor; determine adistance between the location of the first sensor and the location ofthe second sensor in the first position; determine a distance betweenthe location of the second sensor in the first position within thepatient coordinate frame of reference and the location of the secondsensor in the second position within the patient coordinate frame ofreference; determine a distance between the location of the first sensorand the location of the second sensor in the second position by addingthe distance between the location of the first sensor and the locationof the second sensor in the first position and the distance between thelocation of the second sensor in the first position and the location ofthe second sensor in the second position; and cause a display to displaythe distance between the location of the first sensor and the locationof the second sensor in the second position, wherein the controller isconfigured to cause the display to display a count-down of a distanceremaining between at least one of the first sensor and the target or thesecond sensor and the target.
 2. The navigation system according toclaim 1, wherein the tool is an extended working channel, a needle, aguide wire, a biopsy tool, a dilator, or an ablation device.
 3. Thenavigation system according to claim 1, wherein at least one of thefirst sensor or the second sensor is an electromagnetic sensor.
 4. Thenavigation system according to claim 1, wherein the controller isconfigured to cause the display to display of the distance between thetarget and the location of the first sensor.
 5. The navigation systemaccording to claim 1, further comprising an electromagnetic trackingsystem configured to generate an electromagnetic field for calculatingthe patient coordinate frame of reference and electromagnetically trackthe location of the first sensor and the location of the second sensorwhen the second sensor is in the first position within the patientcoordinate frame of reference and when the second sensor is in thesecond position within the patient coordinate frame of reference.
 6. Thenavigation system according to claim 1, wherein the controller isconfigured to determine whether a distance between the location of thesecond sensor in the second position and the target is below apreconfigured threshold.
 7. The navigation system according to claim 1,wherein the display is configured to display an image of a portion ofthe patient's luminal network.
 8. A surgical navigation systemcomprising: a catheter configured to be advanced through a patient'sluminal network, the catheter having a first sensor and defining alumen; and a controller and a memory storing instructions, which whenexecuted by the controller, cause the controller to: track a location ofthe first sensor; track a location of a second sensor when the secondsensor is in a first position within a patient coordinate frame ofreference and when the second sensor is in a second position within thepatient coordinate frame of reference; determine a distance between atarget and the location of the first sensor; determine a distancebetween the location of the first sensor and the location of the secondsensor in the first position; determine a distance between the locationof the second sensor in the first position within the patient coordinateframe of reference and the location of the second sensor in the secondposition within the patient coordinate frame of reference; determine adistance between the location of the first sensor and the location ofthe second sensor in the second position by adding the distance betweenthe location of the first sensor and the location of the second sensorin the first position and the distance between the location of thesecond sensor in the first position and the location of the secondsensor in the second position; and cause a display to display thedistance between the location of the first sensor and the location ofthe second sensor in the second position, wherein the controller isconfigured to cause the display to display a count-down of a distanceremaining between at least one of the first sensor and the target or thesecond sensor and the target.
 9. The surgical navigation systemaccording to claim 8, wherein at least one of the first sensor or thesecond sensor is an electromagnetic sensor.
 10. The surgical navigationsystem according to claim 8, wherein the controller is configured tocause the display to display of the distance between the target and thelocation of the first sensor.
 11. The surgical navigation systemaccording to claim 8, further comprising an electromagnetic trackingsystem configured to generate an electromagnetic field for calculatingthe patient coordinate frame of reference and electromagnetically trackthe location of the first sensor and the location of the second sensorwhen the second sensor is in the first position within the patientcoordinate frame of reference and when the second sensor is in thesecond position within the patient coordinate frame of reference. 12.The surgical navigation system according to claim 8, wherein thecontroller is configured to determine whether a distance between thelocation of the second sensor in the second position and the target isbelow a preconfigured threshold.
 13. The surgical navigation systemaccording to claim 8, wherein the display is configured to display animage of a portion of a patient's luminal network.
 14. The surgicalnavigation system according to claim 8, wherein the first sensor isoperably coupled to a catheter and wherein the second sensor is operablycoupled to a tool configured to be advanced through the catheter.
 15. Asurgical navigation system comprising: a tool configured to be advancedthrough a lumen of a catheter; and a controller and a memory storinginstructions, which when executed by the controller, cause thecontroller to: determine a distance between a target and a location of afirst sensor; determine a distance between the location of the firstsensor and a location of a second sensor in a first position, the secondsensor operably coupled to the tool; determine a distance between thelocation of the second sensor in the first position and a location ofthe second sensor in a second position; determine a distance between thelocation of the first sensor and the location of the second sensor inthe second position by adding the distance between the location of thefirst sensor and the location of the second sensor in the first positionand the distance between the location of the second sensor in the firstposition and the location of the second sensor in the second position;and cause a display to display the distance between the location of thefirst sensor and the location of the second sensor in the secondposition, wherein the controller is configured to cause the display todisplay a count-down of a distance remaining between at least one of thefirst sensor and the target or the second sensor and the target.
 16. Thesurgical navigation system according to claim 15, wherein the controlleris configured to determine whether a distance between the location ofthe second sensor in the second position and the target is below apreconfigured threshold.
 17. The surgical navigation system according toclaim 15, wherein the display is configured to display an image of aportion of a patient's luminal network.